Field
This document relates to a stereoscopic image display and more particularly, to a system and a method for inspecting misalign between a display panel and a film patterned retarder (FPR) in the stereoscopic image display separating polarized lights of a left-eye image and a right-eye image using the FPR.
Related Art
A stereoscopic image display implements a three-dimensional (3D) image using a stereoscopic technique or an autostereoscopic technique.
The stereoscopic technique uses a parallax image of left and right eyes having a great stereoscopic effect, and may be divided into a glasses type and an auto-stereoscopic type. The glasses type displays an image on a direct view display device or a projector by changing a polarization direction of left and right parallax images or in a time division scheme, and implements a stereoscopic image using polarization glasses or shutter glasses. The auto-stereoscopic type generally implements a stereoscopic image by installing optical components such as a parallax barrier and a lenticular lens for separating optical axes of left and right parallax images in a front or rear side of a display screen.
In the glasses type stereoscopic image display, the polarization glasses type requires a polarization separation device, such as a patterned retarder, to be bonded to a display panel. The patterned retarder separates the polarized lights of a left-eye image and a right-eye image displayed on the display panel. A viewer wears polarization glasses when viewing a stereoscopic image on the polarization glasses type stereoscopic image display to see the polarized light of the left-eye image through a left-eye filter of the polarization glasses and the polarized light of the right-eye image through a right-eye filter of the polarization glasses, thereby giving a stereoscopic feeling.
Meanwhile, the shutter glasses type alternately displays a left-eye image and a right-eye image on a display panel without bonding a special polarization separation device to the display panel, opens a left-eye shutter of shutter glasses to be synchronized with the left-eye image, and opens a right-eye shutter of the shutter glasses to be synchronized with the right-eye image. A viewer wears shutter glasses when viewing a stereoscopic image on the shutter glasses type stereoscopic image display to alternately see the left-eye image and the right-eye image which are time-divided, thereby giving a stereoscopic feeling.
In the shutter glasses type stereoscopic image display, since it is unnecessary to mount a polarization separation device in the display panel, a factor of increasing a cost of the display panel is small. However, because there is a need for high cost shutter glasses, manufacturing cost is high. In a 3D image quality side, because the shutter glasses type stereoscopic image display time-divides the left-eye image and the right-eye image at a predetermined time interval, the shutter glasses type stereoscopic image display is weak to flicker and 3D crosstalk. Meanwhile, the polarization glasses type stereoscopic image display includes a polarization separation device such as a patterned retarder mounted in the display panel, a cost of the display panel is slightly increased. However, because low cost polarization glasses are used, a total system cost is lower compared with shutter glassed type. In the image quality side, the polarization glasses type stereoscopic image display simultaneously displays a left-eye image and a right-eye image on the display panel and separates the left-eye image and the right-eye image for each line, flicker and 3D crosstalk levels are lower as compared with the shutter glasses type stereoscopic image display.
The patterned retarder is divided into a glass patterned retarder (GPR) in which a patterned retarder is formed on a glass substrate and a film patterned retarder (FPR) in which the patterned retarder is formed on a film substrate. In recent years, the FPR is capable of reducing a thickness, a weight, and a cost of a display panel as compared with the GPR has been preferred.
In the polarization glasses type stereoscopic image display, a method of aligning and bonding the display panel and the patterned retarder is a very important technique determining 3D display quality. A method of confirming or inspecting a misalign degree between an FPR and a display panel in a manufacturing process of the polarization glasses type stereoscopic image display is not established yet.
Strength of a base film in the FPR is lowered and the FPR is flexible so that a straight degree may be reduced. The FPR having a low straight degree is bent. For this reason, it is difficult to exactly align the FPR having a low straight degree in display lines of a display panel having a high straight degree. If the FPR is misaligned in the display panel due to the FPR having a low straight degree, failure in a viewing angle such as a case where up and down viewing angles of a stereoscopic image display may become narrow or a case where up and down viewing angles differ from each other may occur.